Make End of Rotation the Beginning Rotation of New Animation in Animation Nodes
First, use the Repeat Time node to repeat the the animation every constant duration. Except, we are going to dynamically change the start and end of the animation. Now, if you floor divide the time by the duration, you will get an integer that is constant for the whole duration of the animation and increases by one every time the animation repeats. Since the random nodes are deterministic based on the seed, we can use that integer as the seed of a random node and use its output as the start of the animation, while the end of the animation will be a random node evaluated at the integer plus one as follows:



Note that the node seed is equal in both random nodes.